/*
 * ProGuard -- shrinking, optimization, obfuscation, and preverification of Java bytecode.
 *
 * Copyright (c) 2002-2018 GuardSquare NV
 *
 * This program is free software; you can redistribute it and/or modify it under the terms of the GNU General Public
 * License as published by the Free Software Foundation; either version 2 of the License, or (at your option) any later
 * version.
 *
 * This program is distributed in the hope that it will be useful, but WITHOUT ANY WARRANTY; without even the implied
 * warranty of MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License along with this program; if not, write to the Free
 * Software Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
 */
package proguard.classfile.editor;

import proguard.classfile.*;
import proguard.classfile.attribute.*;
import proguard.classfile.attribute.visitor.AttributeVisitor;
import proguard.classfile.util.SimplifiedVisitor;

import java.util.Arrays;

/**
 * This AttributeVisitor trims the line number table attributes that it visits.
 *
 * @author Eric Lafortune
 */
public class LineNumberTableAttributeTrimmer extends SimplifiedVisitor implements AttributeVisitor {
    // Implementations for AttributeVisitor.

    public void visitAnyAttribute(Clazz clazz, Attribute attribute) {}

    public void visitLineNumberTableAttribute(Clazz clazz, Method method, CodeAttribute codeAttribute,
        LineNumberTableAttribute lineNumberTableAttribute) {
        LineNumberInfo[] lineNumberTable = lineNumberTableAttribute.lineNumberTable;
        int lineNumberTableLength = lineNumberTableAttribute.u2lineNumberTableLength;

        // Overwrite all empty line number entries.
        int newIndex = 0;
        for (int index = 0; index < lineNumberTableLength; index++) {
            LineNumberInfo lineNumberInfo = lineNumberTable[index];

            int startPC = lineNumberInfo.u2startPC;
            int lineNumber = lineNumberInfo.u2lineNumber;

            // The offset must lie inside the code.
            // The offset must be smaller than the next one.
            // The line number should be different from the previous one.
            if (startPC < codeAttribute.u4codeLength &&

                (index == lineNumberTableLength - 1 || startPC < lineNumberTable[index + 1].u2startPC) &&

                (index == 0 || lineNumber != lineNumberTable[index - 1].u2lineNumber)) {
                lineNumberTable[newIndex++] = lineNumberInfo;
            }
        }

        // Clear the unused array entries.
        Arrays.fill(lineNumberTable, newIndex, lineNumberTableAttribute.u2lineNumberTableLength, null);

        lineNumberTableAttribute.u2lineNumberTableLength = newIndex;
    }
}
